I learned about this from watching a video about some "Tech Support" scam (watch the last 10 minutes if you want a good laugh) where one of the tactics used by the scammer is getting the victim to list file associations and reading a GUID and they would pretend it to be the id number of the victims computer.
Here is the association in question:
That got me wondering, what is the purpose of that? Looking at the shell extension it points to gives the description "Compressed (zipped) Folder SendTo Target" and the value NoOpen says "Drag Files onto this icon to compress them.". Renaming a file to this extension on Windows XP results in the file having a compressed folder icon and the file extension hidden (because of the NeverShowExt value I would guess). If I try to open the file Windows just claims that it doesn't have any association. Dragging a file to it, however, creates a new zip file in the same folder containing the dragged file. Note that the content of the .zfsendtotarget file is left completely untouched.
Well it's a curious feature, but strange that you would use a file extension for that. Why it is designed that way is probably only known by a couple of people inside of Microsoft, but has someone seen it used anywhere in windows? Is there some feature somewhere that creates such a file, or some version of windows with a folder containing such a file?